[7257] Add proper pagination to Hosted and Remote Instances pages + N+1 fix for Hosted Instances

[n-lark]

Description

See #7257 (comment)

Related Issue(s)

Resolves #7257

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.57%. Comparing base (b2735a3) to head (1fc84e9).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7353      +/-   ##
==========================================
+ Coverage   76.52%   76.57%   +0.04%     
==========================================
  Files         405      405              
  Lines       20631    20675      +44     
  Branches     4991     5018      +27     
==========================================
+ Hits        15788    15832      +44     
  Misses       4843     4843              

Flag	Coverage Δ
backend	76.57% <100.00%> (+0.04%)	⬆️

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